package com.ecnu.codelearn.thread;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * @Author: 曹培胜
 * @Date: 2021/09/14/13:09
 * @Description: ReadWriteLock
 */
public class ReadWriteLockDemo {
    public static void main(String[] args) {
        MyCache myCache = new MyCache();
        for (int i = 0; i < 5; i++) {
            final int temp = i;
            new Thread(() -> myCache.put(temp + "", temp), String.valueOf(temp)).start();
        }
        for (int i = 0; i < 5; i++) {
            final int temp = i;
            new Thread(() -> myCache.get(temp + ""), String.valueOf(temp)).start();
        }
    }
}

class MyCache {
    private volatile Map<String, Object> map = new HashMap<>();

    //读写锁：更加细粒度的控制
    private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();

    //写入的时候只希望同时只有一个线程写
    public void put(String key, Object value) {
        readWriteLock.writeLock().lock();
        try {
            System.out.println(Thread.currentThread().getName() + "写入" + key);
            map.put(key, value);
            System.out.println("写入ok");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.writeLock().unlock();
        }
    }

    //读可以多个进程读
    public void get(String key) {
        readWriteLock.readLock().lock();

        try {
            System.out.println(Thread.currentThread().getName() + "读取" + key);
            Object o = map.get(key);
            System.out.println("读取ok");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.readLock().unlock();
        }
    }
}
